temper and hardness depth of old and new blades

[Matthew N. Masail]

I just made a few mini planes, using 1 old shoulder plane blade and 1 new one from the mujingfand plane LV sells. I want to make a few more and
thought of cutting down a cheap, old or new 1\2 inch or 5\8inch chisel to get the blades. I was wondering if possibly the new chisels, like narex, are hardened and tempered all the way through? is there a way to know if the old chisels are hardened all the way? I am not interested in doing it myself at the moment.

P7070373 (1280x960).jpgP6300289 (1280x960).jpg

[David Weaver]

If the old chisels are not laminated, they are hardened from top to bottom. Where you'll get a bugaboo will be if you work too close toward the tang on some chisels. A lot of tools are much harder at the business end than the tang end, be they old water hardened chisels or new induction hardened chisels.

[Dave Anderson NH]

Most modern factory made chisels are processed in batches and hardened in temperature regulated furnaces. As a result they are not and can not be differentially hardened like chisels made by hand or forged and heat treated one at a time. It is entirely a matter of efficiency and therefore economics. As an unadvertised safety measure and means of avoiding liability some of the makers choose to make their chisels on the soft side. This certainly makes them less likely to shatter if misused, but it also means they won't hold an edge as long or sometimes at all. This is particularly true of the low end mass market stuff and unfortunately of a couple of the formerly respected and well know British makers now parts of larger companies.

[george wilson]

All chisels,plane irons,and saw blades,unless the former are laminated,are of necessity hardened all the way through. Chisels WERE hardened and tempered by reheating from the tang end,and do get softer towards the tang. Old timers said that chisels were not as good till they were well worn away,meaning that they were TOO HARD at the cutting end to hold a good edge. These days,the whole chisel or plane iron may be tempered the same all over,in a controlled electric furnace,or they may be done the old way. Too hard an edge gets dull sooner because the microscopic edge breaks off,and the tool appears to get dulled.

It is better for the tang ends of chisels to be softer,because they are smaller and thinner there,and could break off if too hard.

This does not pertain to Japanese chisels,which are in a class by themselves.

Saw blades are necessarily softer,being a spring temper,or they would snap off as soon as you managed to bend one in a cut from pushing too hard. While a chisel or plane iron might be 58 Rockwell(or harder,though they should not be),a HARD saw will be 52 Rockwell at most. Most commercial saws,even the best old ones,were softer than that. The 1095 spring steel that the best modern small makers of saws,is 52 Rockwell. It's very noticeably harder to file,but stays sharp a lot longer.

[David Weaver]

Most modern factory made chisels are processed in batches and hardened in temperature regulated furnaces. As a result they are not and can not be differentially hardened like chisels made by hand or forged and heat treated one at a time. It is entirely a matter of efficiency and therefore economics. As an unadvertised safety measure and means of avoiding liability some of the makers choose to make their chisels on the soft side. This certainly makes them less likely to shatter if misused, but it also means they won't hold an edge as long or sometimes at all. This is particularly true of the low end mass market stuff and unfortunately of a couple of the formerly respected and well know British makers now parts of larger companies.

Presume the "good" ones are fully heated and quenched in batches (maybe air quenched). The buck stuff that's still US made is induction hardened, as are the diefenbacher chisels (which appear to be buck). This video is of the buck factory in the US, IIRC. (hardening and tempering at 2:00)

https://www.youtube.com/watch?v=k0JmDbtAFug

You can see that they polish off the bluing that occurs where the chisels aren't hardened, but on the long parers they don't -as mine came with the line still on them (I guess because they don't fit in a machine).

I'd assume this is the case for a lot of the hardware store type chisels, like the stanley fat max, etc, since it's so cheap and fast to induction harden and temper a piece. some HF chisels that I got were pretty cruddy for the first full 1/8th inch, but after that, they were fine.

[Matthew N. Masail]

Thanks! so I guess it's a safe bet to try to get a cheap firmer chisel from the UK and try to make 2 blades out of it.

[george wilson]

Another sloppy use of the term "razor sharp" is found in the video!! Surprising they quench in warm water. Probably because they are making soft chisels that won't "send a splinter into someone's eye". Lawyer incited,no doubt.